Process for inhibiting scale deposition

ABSTRACT

Scale prone waters may be treated with certain sulfonated alkali lignins to inhibit the build up on mineral scale deposits from the scale prone waters upon surfaces in contact with the scale prone waters. Sulfonated alkali lignins are dissolved in the scale prone waters in sufficient concentration to inhibit the formation of mineral scale on the surfaces.

United States Patent 1 Schievelbein et al.

l l PROCESS FOR INHIBITING SCALE DEPOSITION [75] Inventors: Vernon H.Schievelbein; Thomas E.

Sample, Jr., both of Houston, Tex.

[73] Assignee: Texaco Inc., New York, NY.

[22] Filed: June 24, 1974 [21] Appl. No.: 482,282

Related US. Application Data [62] Division of Ser. No. 250,l83, May 4,I972, Pat No.

[52] US. Cl 166/279; 166/310 [51] Int. Cl. E21b 43/00; C02b 5/06 [58]Field of Search.... 166/279, 305 R, 310, 244 C; 252/855 B, 8.5, 180,I8]; 2l0/58 [56] References Cited UNITED STATES PATENTS 2,429,593l0/l947 Case ..l66/31O UX [4 1 June 10, 1975 2,576,386 ll/l95l Bird210/58 X 2,777,8l8 l/l957 Gambill .1 l66/3l0 UX 3,007,864 1 l/l96lAdolphson et al a 252/85 3,020,232 2/1962 Doughty 25218.5 3,l68,5ll2/!965 King et al. 4 4 252/85 X 3,3S4,l7l 5/l968 Parker v l66/274 4/l970Liddell ZSZ/IBO Primary Examiner-Stephen J. Novosad Attorney, Agent, orFirmT. H. Whaley; C. G. Ries; Kenneth R. Priem [57} ABSTRACT 7 Claims,No Drawings PROCESS FOR INHIBITING SCALE DEPOSITION This is a division,of application Ser. No. 250,183, filed May 4, 1972, and now US. Pat. No.3,849,328.

BACKGROUND OF THE INVENTION This invention concerns methods ofinhibiting and/or controlling mineral-scale formation upon surfaceswhich are normally susceptible to scale formation during contact withmineralized waters.

Inorganic mineral scale concretion or the deposition of scale coatingsderived from the extended contact of surfaces normally susceptible toscale formation with hard waters, particularly waters containingalkaline earth compounds, is both wasteful and commonplace. While scaleformation upon metal surfaces presents the more serious problem,non-metallic surfaces including ceramics, glasses and organic polymersmay also undergo scaling.

Particularly troublesome are the tenacious furs"or crusts"that form inoperational processing equipment in continuous and/or prolonged contactwith aqueous solutions of inorganic salts as, for example, alkalineearth sulfates, carbonates and bicarbonates. This type of scaleformation creates serious problems for the petroleum and gas-producingindustries, where the buildup of undesirable inorganic mineral scaledeposits can take place in equipment or tubing of difficult or limitedaccessibility. These include flow lines in both surface and subterraneanlocations, including auxiliary producing equipment, such as heaters,pumps, valves, rods, and the like. In addition, scale formation can alsocause substantial problems in the chemical processing industries, publicutilities, and in other situations where min eral-laden water isprocessed or used, as in heat exchangers, storage vessels, piping,reactors, evaporators, and the like.

Several different explantions have been advanced as to how the formationof mineral scale deposits, such as for example calcium or bariumsulfate, takes place. One mechanism leading to scale formation comesabout from the mingling of a fluid stream containing a substantialconcentration of an anion or cation with another stream containingantagonistic counter ions. An illustration of this mechanism would be acase in which one process stream containing a soluble calcium compoundcontacts another stream containing a soluble sulfate compound to causeprecipitation of calcium sulfate. Should the mixing of such incompatiblewaters take place in a well bore, the result may be deposition of acrust of calcium sulfate which, if allowed, can build up on the surfaceof submerged equipment such as tubing, and may even choke off fluid flowby diminution of utilizable diameter unless corrective descalingmeasures are undertaken. In the case of heat exchange equipment, themineral scale deposition insulates the equipment from the source or sinkof heat and increases the cost of operation and may cause extensivemaintenance or downtime and increased operational costs.

Another cause of mineral scale formation arises from aqueous solutionsof inorganic materials having an inverse solubility curve, that is, asolubility which decreases as the temperature increases. An excellentexample of this is calcium sulfate, whose solubility in water decreaseswith increased temperature. In these instances the solution immediatelyadjacent to the heating surface reaches saturation the most quickly,

dropping calcium sulfate at this juncture which is held tenaciously tothe heating surface.

Yet another cause of scale formation is attributable to precipitation ofscale material from supersaturated solutions, of which the precedingexample is a special case. When temperature and/or pressure changesoccur, or the concentration of some solubilizing substances issubstantially decreased, this change of conditions can result in scaleformation on the tubing or other equipment being operated.

Whatever the reason or reasons for scale formation may be, as outlinedabove, it is a troublesome and expensive process that can lead tocostly, unscheduled maintenance and even to the breakdown of operationalunits. For these reasons, a number of remedial measures have beenresorted to, both for the removal of scale and mitigation of itsformation.

Scale is ordinarily removed by either chemical or mechanical methods, ora combination of both methods. In chemical descaling procedures, theproblem is to find a material that will dissolve or loosen the mineralscale without attaching the underlying substrate.

Inhibited hydrochloric acid has proved useful in instances where thescale is acid soluble, as is the case with calcium carbonate scale.Unfortunately, however, many mineral scales, such as those of calciumand barium sulfates, are not appreciably soluble in acids: Calciumsulfate scale can sometimes be dissolved or loosened by treatment withammonium salts, polyphosphates, or hydroxides, often followed by acidwashing.

Mechanical descaling procedures are often resorted to employing suchdevices as scrapers, brushes, highpressure abrasive jets, and the like,but these methods are tedious, expensive, and of restrictedapplicability.

It is an object of this invention to provide a method whereby theseharmful scale deposits are inhibited from forming on a surface, thusavoiding the problems of removal.

Scale prone waters as used herein refers to aqueous solutions of mineralcompounds which tend to form scale on surfaces contacting the waters.

SUMMARY OF THE INVENTION The invention is a method of inhibiting theformation of mineral scale upon a substrate surface in contact withscale prone waters. The method comprises dissolving in the scale pronewaters about 0.0005 to about 0.01 weight percent of sulfonated alkalilignin compounds. The invention is also the scale inhibiting solution.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Lignin is second only tocellulose as the principal constituent in wood. Generally, lignin is acomplex phenolic polyether containing many different functional groups,including carboxyls, carbonyls and alcoholic and phenolic hydroxyls.Lignins and their derivatives are described in Kirk-Othmer, Encyclopediaof Chemical Technology, Second Edition, Volume 12 beginning at page 36].Certain lignin derivatives are useful in the process of our inventionare manufactured by a particular process which distinguishes them overother lignins and lignin derivatives which have been found to be lessuseful as scale inhibitors.

Very briefly, the above publication describes two very broad classes oflignin derivatives: sulfite lignins and alkali lignins.

The difference in the lignins exists because of the lignin derivativefalls within the class of sulfonated alkali lignins preferred for use inour invention. The following Table I gives data concerning theproperties of typical commercially available sulfonated alkali ligninsmethod of extraction of lignin material from woody 5 suitable for use inthe process of our invention.

TABLE 1 TYPlCAL PROPERTIES OF SULFONATED ALKALI LIGNINS PROPERTY A B C DE F G H J Degree of Sulfonation 2.0-2.5 2.0-2.5 l.9 2.4 l.6 2.5-3.03.5-4.0 0.8-l.| 2.0 3.7 pH l l.0l2.0 8.0-9.5 9.29.8 ll 7.5-9.0 4.5-6.5l0.2l 1.2 10.5 ll Ash 30-36 30 36 lS-23 l8-23 l-3 l7-22 pH ofPrecipitation in 5% Solutions 0.5 0.5 0.5 v 5.0 3 5 Type Cation Na Na NaNa Na NH, Na Na* Na Number of sulfonule groups per 1.000 unit weight oflignin.

materials. The lignin derivatives which are preferred for the process ofour invention are made by sulfonation of the so called alkali lignins.

The sulfonated alkali lignins useful in our invention are readilyavailable commercially from various sources including but not limited toWest Virginia Pulp and Paper Company of North Charleston, South Carolinaunder the tradename REAX 80s. Their general method of preparation isdescribed in the Enclyclopedia of Chemical Technology referred to above.Briefly, the sulfonated alkali lignins useful in ourinvention areprepared as follows according to the above publication.

Wood chips are cooked with a 10% solution ofa mixture of sodiumhydroxide with about mole percent of sodium sulfide. The lignin withwood is modified into a sodium compound, often termed sodium lignate oralkali lignin, which is very soluble in the strongly alkaline solution.These alkali lignins are removed from solution by lowering the pH whichprecipitates out the alkali lignins. These unsulfonated alkali ligninsare sold under various tradenames including lndulin Also, these alkalilignins are used to prepare the sulfonated derivatives useful in ourinvention. Methods of sulfonation are known to those skilled in the art.One typical method involves treating the alkali lignins with a solutionof alkali sulfites at elevated temperature and pressure. The degree ofsulfonation may be controlled to provide a variety of sulfonated alkalilignins useful in the process of our invention.

The degree of sulfonation and molecular weight of the sulfonated alkalilignins have no discernable effect on scale inhibiting performance.

Sulfite lignins are not preferred in the process of our invention.Sulfite lignins are generally made by cooking wood chips under pressurein a solution of sulfurous acid and calcium, magnesium, sodium, orammonium bisulfate. This process converts insoluble lignins to solublelignosulfonic acid. The lignosulfonic acid or calcium, magnisium,sodium, or ammonium salts of the lignosulfonic acids are available undervarious trade names including Marasperse, Orzan, Toranil, and Ray flo.

To reiterate, only sulfonated alkali lignins are useful in the processof our invention. Other lignin derivatives such as alkali lignins, andsulfite lignins do not impart unusaul scale inhibiting properties toaqueous solutions and are not included within the scope of ourinvention.

The structure of the preferred sulfonated alkali lignins is not know,but one skilled in the art may determine from a description of themanufacturing technique used to prepare a lignin derivative whether thatThe sulfonated alkali lignins will inhibit the formation of mineralscale if they are introduced into the scale prone waters by anyconvenient means in an amount sufficient to provide about 0.0005 toabout 0.01% of the said lignin derivative by weight. For instance,aqueous solutions containing from about 1 to about 50% by weight ofthese sulfonated alkali lignins can be prepared and perhaps stored andlater added to scale prone waters to provide a total concentration offrom about 0.0005 to about 0.01% by weight. These concentrate solutionsof the sulfonated alkali lignins of our invention may be added directlyto scale prone waters and should be mixed in any convenient way known tothe art in order to provide uniform dispersion. The sulfonated alkalilignins may also be added to scale prone waters in any other convenientconventional manner including adding the solid sulfonated alkali lignindirectly to the scale prone water to be treated and then providing formixing to cause dispersion of the material in the water. Uniformdispersion of the sulfonated alkali lignin is necessary to insure that asufficient amount of the lignin derivative is mixed with the water atpoints where scale deposition is normally likely to occur.

The resulting scale inhibiting solution may be used to inhibit scaleformation on the parts of equipment such as pumps, boilers, piping andother equipment exposed to scale prone waters. Scale deposition uponwell casing, tubing, pumps, and related equipment may be encounteredwhere scale prone water is injecting into subterranean formations. Inthis case the method of this invention will inhibit scale deposition ifsufficient amounts of sulfonated alkali lignins are dispersed into thescale prone water to be injected.

Where subterranean petroleum reservoirs produce scale prone water inaddition to petroleum, scale deposition will be inhibited by injecting asolution of sulfonated alkali lignin solution into the formation aroundthe well bore and then resuming production. The produced scale pronewater will carry with it the sulfonated alkali lignin previouslyinjected. When the sulfonated alkali lignin is depleted theinjection-production cycle should be repeated.

EXAMPLE 1 The following data in Table II demonstrates the superiority ofthe sulfonated alkali lignins over conventional materials marketed asscale control chemicals. Examination of the data in Table II revealsthat all sulfonated alkali lignins tried prevented scale deposition andare superior to most recognized scale control chemicals.

The following procedure was used in the evaluation: Into a 1000 ml.beaker, there was placed sufficient calcium sulfate and sodium chloride(obtained by mixing solutions of calcium chloride and sodium sulfate) toproduce therein an aqueous solution containing 10,000 parts per millionof calcium sulfate and 50,000 parts per million of sodium chloride. Apreweighed metal rotor attached to an externally provided mechanicalstirring device was immersed in the test solution for a period of 24hours. The solution was maintained at a temperature of 104F. during thetest period. At the end of the 24 hours, the rotor was removed from thesolution and from the stirrer, dried and re-weighed The difference inweights of the rotor was taken as the amount of calcium sulfate scaledeposited.

We claim 1. A method for inhibiting the formation of mineral scale uponsurfaces in contact with scale prone waters, the surfaces including awell casing and related surface and subsurface equipment for a welldrilled to and in fluid communication with a subterranean formationwherein the well and related equipment is used to inject the scale pronewaters into the subterranean formation comprising dissolving sulfonatedalkali lignins in the scale prone waters before the aqueous solutioncontacts the well casing and related equipment.

2. A method as in claim 1 wherein the sulfonated alkali lignins have adegree of sulfonation from about 0.8 to about 4.0.

3. A method as in claim 2 wherein the sulfonated al- -kali lignins arepresent in an amount from about 0.0005

"Product of West Virginia Pulp & Paper Co. Westvaco PulychemicalsProducts 'Product of Champion Chemicals. Inc.

"Pruduct of Milchem Inc.

'Product of Champion Chemicals, Inc.

""Product of Texaco. lnc.

EXAMPLE 2 Cone. of

Weight of Scale Deposited Additive (pp 0 100 Control 1 (No Additive]1.5287 Control 2 (No Additive) 1.1 189 Control 3 (No Additive) l.6l95

Sulfite Lignin 1 0.6576 Sulflte Lignin 2 1.1480 Sulfite Lignin 3 1.0463Unsulfonated Alkali Lignin 1 0.7063 Unsulfonated Alkali Lignin 2 1.01 13Unsulfonatcd Alkali Lignin 3 0.9917

to about 0.01% by weight.

4. A method for inhibiting the formation of mineral scale upon surfacesin contact with scale prone waters, the surfaces including a well casingand related surface and subsurface equipment for a well drilled to andin communication with a subterranean formation wherein the well andrelated equipment is used to produce fluids from the subterraneanformation including scale prone waters comprising injecting an aqueoussolution of sulfonated alkali lignins through the well and into thesubterranean formation and producing fluids from the subterraneanformation.

5. The method of claim 4 wherein the fluids produced from thesubterranean formation comprise petroleum and scale prone waters.

6. The method of claim 4 wherein the sulfonated alkali lignins arepresent in the produced fluids in an amount from about 0.0005 to about0.01% by weight.

7. The method of claim 6 wherein the sulfonated alkali lignins have adegree of sulfonation from about 0.8

to about 4.0.

1. A METHOD FOR INHIBITING THE FORMATION OF MINERAL SCALE UPON SURFACESIN CONTACT WITH SCALE PRONE WATERS, THE SURFACES INCLUDING A WELL CASINGAND RELATED SURFACE AND SUBSURFACE EQUIPMENT FOR A WELL DRILLED TO ANDIN FLUID COMMUNICATION WITH A SUBSTERRANEAN FORMATION WHEREIN THE WELLAND RELATED EQUIPMENT IS USED TO INJECT THE SCALE PRONE WATERS INTO THESUBTERRANEAN FORMATION COMPRISING DISSOLVING SULFONATED ALKALI LIGININSIN THE SCALE PRONE WATERS BEFORE THE AQUEOUS SOLUTION CONTACTS THE WELLCASING AND RELATED EQUIPMENT.
 2. A method as in claim 1 wherein thesulfonated alkali lignins have a degree of sulfonation from about 0.8 toabout 4.0.
 3. A method as in claim 2 wherein the sulfonated alkalilignins are present in an amount from about 0.0005 to about 0.01% byweight.
 4. A method for inhibiting the formation of mineral scale uponsurfaces in contact with scale prone waters, the surfaces including awell casing and related surface and subsurface equipment for a welldrilled to and in communication with a subterranean formation whereinthe well and related equipment is used to produce fluids from thesubterranean formation including scale prone waters comprising injectingan aqueous solution of sulfonated alkali lignins through the well andinto the subterranean formation and producing fluids from thesubterranean formation.
 5. The method of claim 4 wherein the fluidsproduced from the subterranean formation comprise petroleum and scaleprone waters.
 6. The method of claim 4 wherein the sulfonated alkalilignins are present in the produced fluids in an amount from about0.0005 to about 0.01% by weight.
 7. The method of claim 6 wherein thesulfonated alkali lignins have a degree of sulfonation from about 0.8 toabout 4.0.